Let's dive into this subtraction. We'll start with 303378 and subtract 78145 from it.

Step 1: We'll start by subtracting the digit 5 and the borrow 0 from 8 in column 1 and get 3.
3 is the first digit of our result.

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 7 in column 2 and get 3.
3 is the next digit of our result.

Step 3: We'll start by subtracting the digit 1 and the borrow 0 from 3 in column 3 and get 2.
2 is the next digit of our result.

Step 4: We'll start by subtracting the digit 8 and the borrow 0 from 3 in column 4 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 5: We'll start by subtracting the digit 7 and the borrow 1 from 0 in column 5 and get -8.
We add -8 to 10 and get 2 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 3 in column 6 and get 2.
2 is the next digit of our result.

So, 303378 - 78145 = 225233.